1. Field of the Invention
This document relates to a method for coding and decoding a moving picture.
2. Description of the Related Art
A scheme of compressing (coding) a moving image has been advanced from MPEG1, 2, 4 to H.264 (MPEG4 part 10, AVC). After MPEG2 was developed for compression of a high-quality moving image in a digital television (DTV), MPEG4 was developed to enable objects to be respectively compressed on the basis of H.263 that is dedicated mainly for communication purposes. MPEG4 is so excellent that it is adopted as the standard in almost all fields of mobile technology.
Meanwhile, H.264 requires about 5-50 times the calculation of MPEG4 while providing a higher coding rate than MPEG4. Accordingly, H.264 is used for digital mobile broadcasting (DMB) by employing only a decoder having a relatively small amount of calculation.
Recently, researches are actively conducted to develop new image codec algorithms capable of providing a high coding rate with a relatively small amount of calculation.
An example of the new image codec algorithms is a moving image codec using a wavelet transform scheme.
In comparison with the existing MPEG using a discrete cosine transform (DCT) scheme, the wavelet transform type image coding scheme can provide an excellent scalability and image quality. Therefore, the wavelet transform type image coding scheme is considered as the next generation image codec.
The wavelet transform type moving image codec basically performs a wavelet transformation on one frame and then encodes the resulting value.
However, the wavelet transformation scheme does not perform a coding operation on the time axis and thus has a lower coding rate than MPEG4. To overcome this drawback, there is proposed a three-dimensional (3D) wavelet coding scheme for performing a wavelet transformation on a group of frames for the time axis.
However, since a group of frames are simultaneously coded for a wavelet transformation, one frame can be decoded only when the entire frame group is decoded. That is, the entire frame group must be decoded so as to decode only one frame, and the first frame of the frame group can be displayed only after the entire frame group is decoded. Therefore, it takes a long time to display the first frame by the 3D wavelet transformation.
In this manner, the coding rate and the display time for the first frame varies depending on how many frames are included in the frame group in the moving image codec using the 3D wavelet transformation.
When many frames are included in the frame group for a high coding rate, it takes a long time to display the first frame. On the contrary, when a few frames are included in the frame group, the coding rate is undesirably reduced.